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    This data set has trawl catch weight and biological measurements from the 2nd leg of the Icelandic part of the International Ecosystem Summer Survey in Nordic Seas (IESSNS). The survey area was from the coast, over the shelf edge and into the deep-water basins south and west of Iceland, defined as IESSNS strata 5, 6, and 12, and stratum boundaries (black solid line) are displayed on attached map "IESSNS 2018.png". The survey period is July 19th to August 1st, 2018, and samples were collected at 34 trawl stations (blue symbol on attached map "IESSNS 2018.png"). A specifically designed scientific trawl, called Multpelt832 (ICES, 2013a-b, Valdemarsen et al 2014) with cod-end mesh size of 50 mm, was use at all 34 stations. Trawl depth ranged from surface (trawl headline in surface) to 400 m depth. All trawl catch is identified to lowest possible taxonomic level, total weight of each species recorded and length of 20-50 specimen per species measured. For blue whiting (Micromesistius poutassou) more biological measurements are provided such as weight, sex, maturity, age, and stomach weight. For age determination, the otolith was extracted whole from the blue whiting at sea and read whole under a dissecting microscope on land by an experienced age reader part of the ICES framework. Gonad maturity stage was visually estimated at sea during sampling by an experienced technician. The maturity stages are 1-7, where 1 is immature, 2 is beginning to mature or beginning to recovering from previous spawning event, 3 is maturing, 4 is maturing, 5 is getting fully mature, 6 is spawning, and 7 has finished spawning. In total measurements are provided for 1451 specimen. Each specimen is one row in the data set file. At ten stations (345, 356, 366, 369, 372, 378, 381, 390, 394, 395) Natantia and Scyphozoa specimen could not be identified to species, hence no individual length measurements are provided but total weight of catch per taxon is provided. Information for three pelagic fish species is excluded from the data set and these species are mackerel (Scomber scombrus), herring (Clupea harengus) and lump fish (Cyclopterus lumpus). For detailed information about the survey see the survey report (in English): https://www.hafogvatn.is/is/midlun/utgafa/haf-og-vatnarannsoknir/results-of-the-icelandic-part-of-the-international-ecosystem-summer-survey-in-nordic-seas-iessns-in-2018-on-rv-arni-fridriksson-hv-2019-21. Various information are provide about the trawling operation, weather, position, date and time.The data is provided by the Marine and Freshwater Research Institute (MFRI) in Reykjavik, Iceland.